Measuring rotary motions, and, in particular, the speed and the rotational behavior of individual wheels on a vehicle is of great importance in connection with automotive vehicle control systems such as systems for anti-lock control brake systems, traction slip control, and suspension control, etc. Sensors for these types of applications must be durable, reliable, inexpensive to manufacture, and easy to assemble, diagnose, replace, and maintain.
To position a sensor relative to a vehicle wheel, the sensor is typically integrated into a dust cap which is mounted over the end of the vehicle's bearing assembly. The dust cap not only protects the vehicle bearing and its components from damage, it also provides a method of positioning and securing the wheel speed sensor relative to the vehicle wheel so that it can monitor and measure the wheel's rotational speed. Usually a tone wheel, having parallel windows or gear teeth or some other position-identifying features, is fixedly attached to the vehicle shaft and positioned in the interior cavity of the dust cap. The wheel speed sensor is located relative to the tone wheel so as to sense the speed of the rotating parallel windows, gear teeth, or other position-identifying features of the tone wheel. The wheel speed sensor is typically mounted to the dust cap with a bolt or is integrally molded into the dust cap.
Wheel speed sensors can malfunction from time to time, requiring them to be serviced or replaced. Whether wheel speed sensors are attached to the dust cap with a bolt or are integrally molded into the dust cap, servicing of the sensors requires that the dust cap be removed from the shaft. Removal of the dust cap requires the disassembling of several components, and disturbs the bearing assembly, exposing it to possible damage. Moreover, the dust cap is invariably damaged during disassembly and requires replacement after the wheel speed sensor is serviced.